ASTM A203 Grade A and Grade D are nickel-alloy steel plates for low-temperature welded pressure vessels, differing mainly in nickel content, where Grade A typically has ~2% Ni (often "2% Ni steel") and Grade D has ~3.5% Ni (often "3.5% Ni steel"), providing superior toughness and impact resistance at cold temperatures, crucial for industries like oil, gas, and chemical processing for equipment like scrubbers and storage tanks.
Chemical Composition of A203 Grade A
A203 Grade AChemical Composition | |||||
Grade | The Element Max (%) | ||||
C | Si | Mn | P | S | |
A203 Grade A | 0.17 | 0.13-0.45 | 0.78-0.88 | 0.035 | 0.035 |
Chemical Composition of A203 Grade D
A203 Grade D Chemical Composition | |||||
Grade | The Element Max (%) | ||||
C | Si | Mn | P | S | |
A203 Grade D | 0.17 | 0.13-0.45 | 0.70-0.80 | 0.035 | 0.035 |
Mechanical Property of A203 Grade A
Mechanical Property of A203 Grade A steel plate | A203 Grade A |
Tensile strength, kis [MPa] | 65-85 [450-585] |
Yield strength, min, kis [MPa] | 37 [255] |
Elongation in 8 in. [200 mm], min, % | 15 |
Elongation in 2 in. [50 mm], min, % | 19 |
Mechanical Property of A203 Grade D
Mechanical Property of A203 Grade D steel plate | A203 Grade D |
Tensile strength, kis [MPa] | 65-85 [450-585] |
Yield strength, min, kis [MPa] | 37 [255] |
Elongation in 8 in. [200 mm], min, % | 19 |
Elongation in 2 in. [50 mm], min, % | 23 |
Key Differences & Similarities:
Material Type: Both are nickel alloy steels under ASTM A203, designed for low-temperature service.
Nickel Content:
Grade A: About 2% Nickel (2.03-2.57%).
Grade D: About 3.5% Nickel (3.0-4.0%).
Performance: Higher nickel content (Grade D) enhances low-temperature toughness and fracture resistance more significantly than Grade A, making Grade D suitable for even colder applications like methanol scrubbers.
Applications: Both used in pressure vessels, but Grade D's improved cryogenic properties suit severe low-temp roles.
Heat Treatment: Both typically require normalizing, with Grade F (another A203 grade) sometimes quenched and tempered.
